Angular position measuring devices, also frequently referred to as shaft encoders, are used for measuring rotary motions of a rotationally mounted member, particularly a shaft, over one or more revolutions (multiturn functioning). In so doing, the rotary motion is recorded incrementally or absolutely. In conjunction with gear racks and gear wheels or with threaded spindles, linear motions can also be measured by an angular position measuring device.
In order to adjust alignment errors, for example, between the shaft of an angular position measuring device and the shaft to be measured, couplings are frequently used. The shaft of the angular position measuring device can be fitted rigidly to the shaft to be measured. The coupling compensates for the axial and radial relative motions between the shaft to be measured and the measuring unit of the coupling, and it reduces the forces generated thereby. In order to avoid corruption of the measuring results, the respective coupling should behave in a manner that is resistant to rotation or is rotationally rigid.
An angular position measuring device is described in German Published Patent Application No. 103 43 727 in which a housing is able to be rigidly mounted on a machine part. A shaft is rotatably supported relative to the housing. For the compensation of mechanical inaccuracies, an elastic torque support is provided within the housing of the angular position measuring device. In order to stop the spring motions of the torque support, especially during the assembly or attachment of the angular position measuring device, the shaft is fixed with respect to the housing.